High-Performance Type for a Motor Vehicle

ABSTRACT

A tyre for a motor vehicle, in particular a high-performance tyre, is provided with a tread having an overall width. The tread includes first and second circumferential grooves which separate a central region from first and second shoulder regions. The tread includes a circumferential cut in the first shoulder region at a distance from the first circumferential groove; and a plurality of circumferentially repeated transverse groove modules. A first shoulder portion of each transverse groove module includes at least one main transverse groove which includes a first substantially rectilinear portion inclined by a first angle with respect to a radial plane, a second substantially rectilinear portion inclined by a second angle with respect to the radial plane and arranged between the circumferential cut and the first circumferential groove, and a first curve portion connecting the first and the second substantially rectilinear portions.

The present invention relates to a tyre for a motor vehicle, inparticular to a high-performance tyre.

Motor vehicle tyres having a tread provided with blocks delimited bycircumferential grooves extending in a substantially longitudinaldirection and by transverse grooves extending in a substantially axialdirection are known. The blocks resulting from the intersection of saidgrooves are formed in various suitably designed shapes and are arrangedin adjacent circumferential rows, each of which is located between twosuccessive circumferential grooves.

The circumferential grooves may influence the directional and travelstability properties of the tyre in relation to the lateral (slip)thrusts directed parallel to the rotation axis of the tyre.

The transverse grooves, in turn, may influence the traction propertiesof the tyre, namely its capacity to transmit efficiently to the roadsurface the tangential thrusts parallel to the direction of travelduring acceleration and braking of the motor vehicle.

The circumferential grooves may also influence the draining of the waterin the area making contact with the road surface-(footprint area) duringtravel on a wet road surface.

Furthermore, the presence of transverse and circumferential groovesinfluences the rolling noise of the tyre. In fact, one of the maincauses of noisiness is the continuous succession of impacts of the edgesof the blocks on the road-surface.

A further cause of noisiness consists in dragging of the blocks on theroad surface when they enter and leave the area of contact with the roadsurface. This dragging is due essentially to the deformation of thetread both when the tyre is flattened against the road surface and whenit recovers its inflated condition, as it leaves the area of contactwith the road surface.

The deformations of the tread when coming into contact with and leavingthe area of contact with the road surface also produce a cyclicalvolumetric variation of the grooves which delimit the blocks and aconsequent cyclical action of compression and expansion of the airtrapped inside the grooves. These phenomena of compression and expansionof the air increase the rolling noise of the tyre.

Various measures which tend to limit the rolling noise of a tyre areknown. One of these consists in providing the blocks with differentlongitudinal dimensions by adopting two or more different-pitch valuesdistributed in circumferential succession—called “pitch sequence”—suchas to provide the maximum possible lack of uniformity over thecircumferential extension of the tread. The aim is to distribute theacoustic energy due to the impacts and dragging of the blocks over awide spectrum of frequencies, thus avoiding concentrating it in aspecific frequency and producing bothersome noise.

The noisiness of a tyre, measured in accordance with New Dir. 2001/43/ECAug. 4, 2001, is considered unacceptable when it exceeds the followinglimits:

tyre width 145 mm 72 dB(A) tyre width >145 and 165 mm 73 dB(A) tyrewidth >165 and 185 mm 74 dB(A) tyre width >185 and 215 mm 75 dB(A) tyrewidth >215 mm 76 dB(A)

The noisiness of tyres is a problem which is difficult to solve becausesome measures which tend to reduce it adversely affect the directional,traction and water drainage properties.

EP 1 189 770 B1 describes a high performance tyre for a motor vehicleprovided with a tread having an overall width L and comprising two deepcircumferential grooves which separate a central region from two lateralshoulder regions, said shoulder regions being provided with shoulderblocks, the sum of the widths of said lateral shoulder regions beingequal to or less than 60% of the overall width L, the width of each ofthe shoulder regions being not less than 20% of said overall width L,each of said circumferential grooves being adjacent, on the side furtherfrom the central region, to a continuous track from which are branchedtransverse grooves which delimit said shoulder blocks, said continuoustrack terminating in a continuous wall which forms a lateral wait ofsaid circumferential groove, characterized in that said continuouslateral wall of at least one circumferential groove has a profile, in aradial plane, which is more inclined, with respect to a center-line axisof said circumferential groove, than the profile of the facing lateralwall of said circumferential groove, and in that the blocks of thecentral rows are separated by transverse grooves having a bottom wallwith a shaped profile of variable depth.

EP 0 812 709 describes a tyre having a tread comprising two regions atleast one of which is provided with a plurality of inclined maingrooves, each of which comprises a segment with a steep inclination anda segment with a slight inclination. A lateral band of the two regionshas an auxiliary groove with a steep inclination communicating with twoadjacent, inclined, main grooves and an auxiliary groove with a slightinclination, situated between the two adjacent, inclined, main grooves.In a first embodiment, the inclined main grooves extend from acircumferential groove close to the equatorial plane of the tyre, whilein a second embodiment they have a blind bottom. In a third embodiment,the steeply inclined segments of two adjacent, inclined, main groovesare joined by a thin transverse groove.

EP 0 867 310 describes a tyre comprising blocks formed in a treadportion by means of a plurality of circumferential grooves and aplurality of directionally inclined grooves. At least some of thedirectionally inclined grooves extend from a circumferential grooveclose to the equatorial plane of the tyre and extend towards one end ofthe area of the tread making contact with the ground. Each, of theblocks has an angled portion which forms an acute angle of 10°-60defined by a circumferential groove and a directionally inclined groove.The surface of the angled portion of the block is chamfered over adistance of 10-30 mm from a tapered end thereof in a longitudinaldirection so as to vary gradually towards, a portion of larger width.

Nowadays high performance vehicles more and by electronic systems. Suchsystems manage different driving conditions and modify the dynamicbehavior of the vehicle for improving, for instance, stability, brakingand acceleration performances thereof. In this scenario, highperformance tyres are required to work in a different way with respectto tyres of the past and need to be redesigned (in terms of treadpattern and internal, structure thereof) so as to meet the relevantchanges introduced in the vehicle behavior by the electronic systems.

It can be pointed out that high performance vehicles have a negativecamber while running under normal driving conditions, but have null orpositive camber when high lateral accelerations and/or quick loadtransfers, occur. Since the electronic systems sensibly and activelyintervene on the vehicle; behavior, the tread pattern designs have, totake into account said fact.

In the following description, the terms “HP” (High Performance) or “UHP”(Ultra High Performance) tyres indicate tyres which are suitable forapplications involving high operating speeds (e.g. higher than 200 km/h)and/or extreme driving conditions. In particular the terms HighPerformance or Ultra High Performance tyres are intended to indicatetyres which belong to Classes “H” and “V” (maximum speed over 210 Km/h)and to Classes “W” and “Y” (maximum speed over 240 Km/h).

The Applicant has perceived the necessity of improving the handlingproperties of a high performance tyre, in particular (but notexclusively) of an asymmetric tyre, meanwhile ensuring good aquaplaning,grip and noiseness properties.

In particular, the Applicant has perceived the necessity of increasingthe lateral stiffness of at least one shoulder region, particularly ofthe external one, of a high performance tyre so as to withstand therelevant lateral thrusts which arise, for instance, during high speedcornering maneuvers or in extreme driving conditions, e.g. while runningat the limit of adherence.

Even though the maximum lateral stiffness can be achieved by a slicktyre (wherein the maximum amount of rubber contacts the rolling surfacein the tyre footprint area), it is apparent that such a technicalsolution is not acceptable for a tyre which is required to be used onroads and not on race circuits since a slick tyre has no aquaplaningperformance at all.

On the contrary, even though the aquaplaning performances can beimproved by providing at least one longitudinal groove in the externalshoulder region, this would generally lead to a reduction of the lateralstiffness since a lower amount of rubber would be in contact with therolling surface. However, this reduction is at least partiallycompensated by a hinge effect which causes an increase of the tyrefootprint area in correspondence of the zone adjacent to said at leastone longitudinal groove.

The Applicant has thus perceived the necessity of providing a tyre whichcombines high performances in terms of handling, especially lateralstiffness, and aquaplaning, without negatively affecting grip and noisecharacteristics.

The Applicant has found that such a combination of performances can beadvantageously achieved by providing the tyre tread pattern with atleast two circumferential grooves which define two distinct shoulderregions, one of said shoulder regions being provided with a shouldercircumferential cut—located at a certain distance from the adjacentcircumferential groove—and with a plurality of main transverse groovesthat are positioned in the tread area comprised between saidcircumferential cut and the circumferential groove adjacent to saidshoulder region. According to the present invention, said shoulderregion is the external shoulder region (i.e. external with respect tothe vehicle side, as described in the following of the presentdescription) since, as mentioned above, during high speed corneringmaneuvers, the external wheel, and thus the external shoulder region, isrequired to support a prevailing portion of the vehicle load.

According to the present invention said main transverse grooves areremarkably inclined (with respect to a radial plane of the tyre) towardssaid circumferential groove so as to provide the tyre with good handlingperformances as well as with good aquaplaning performances.

In fact, as far as the handling performances are concerned, the inclinedmain transverse grooves confer a suitable flexibility to the shoulderregion in the lateral direction so that the tyre footprint area isadvantageously increased. Meanwhile, said inclined main transversegrooves do not negatively affect the lateral stiffness of the shoulderregion thanks to the positive contribution of the hinge effect mentionedabove.

Furthermore, the inclination of the main transverse grooves compensatesthe ply steer force which is generated—in each tyre—by the inclinationof the metallic cords of the tyre outermost belt layer, said ply steerforce being directed along the cords inclination. The main transversegrooves according to the tread pattern of the present invention allow tobalance said ply steer forces so that the equilibrium of the tyre isadvantageously increased.

As far as the aquaplaning performances are concerned, the inclined maintransverse grooves contribute in discharging the water from the tyrefootprint area and thus support the discharging effect carried out bythe circumferential grooves. In particular, while the circumferentialgrooves discharge the water from the central rear (with respect to therolling direction) side of the tyre footprint area, the main-transversegrooves discharge the water from a lateral (external) side of the tyrefootprint area. This effect remarkably contributes in increasing theaquaplaning performance of the tyre, especially the aquaplaningperformance when high speed cornering maneuvers are performed.

Moreover, the Applicant has found that the shoulder circumferential cutof the tread pattern of the present invention has a positive hingeeffect which contributes in increasing the flexibility of the tyreshoulder region and thus, as mentioned above, the handling performanceis advantageously increased.

Furthermore, the tread pattern of the present invention allows toachieve good noisiness performances both inside and outside a vehicle,with an excellent performance on wet and dry road surfaces at highspeeds.

According to the present invention, a tyre for a motor vehicle, inparticular a high-performance tyre, is provided, said tyre beingprovided with a tread having an overall width L. The tread comprises afirst and a second circumferential grooves which separate a centralregion from a first and a second shoulder regions. According to theinvention, the tread comprises a circumferential cut in the firstshoulder region at a distance from said first circumferential groove;and a plurality of circumferentially repeated transverse groove modules.A first shoulder portion of each transverse groove module comprises atleast one main transverse groove which comprises: a first substantiallyrectilinear portion inclined by a first angle with respect to a radialplane, a second substantially rectilinear portion inclined by a secondangle with respect to the radial plane and arranged between thecircumferential cut and the first circumferential groove, and a firstcurve portion connecting the first and the second substantiallyrectilinear portions.

Preferably, the main transverse groove further comprises a second curveportion connecting the second substantially rectilinear portion to thefirst circumferential groove.

The second curve portion, preferably, has a depth that is lower than adepth of said second substantially rectilinear portion.

Preferably, the first shoulder region has a width that is between 25%and 35% of the overall width.

Preferably, the distance between the circumferential cut and the firstcircumferential groove is between 25% and 35% of a width of the firstshoulder region.

According to an embodiment of the invention, the second substantiallyrectilinear portion ends at a distance from said first circumferentialgroove that is from about 5% to about 40% of the distance between thecircumferential cut and the first circumferential groove.

According to an embodiment of the invention, the second substantiallyrectilinear portion ends at a distance from the first circumferentialgroove that is between about 30% and 40% of a width of the firstcircumferential groove.

Preferably, the first angle ranges from 3° to 10°. More preferably, itranges from 7° to 9°.

Preferably, the second angle ranges from 105° to 130°. More preferably,it ranges from 110° to 120°.

According to the present invention, the main transverse groove furthercomprises a tail connected to the first substantially rectilinearportion.

Preferably, the circumferential cut comprises cut portions having afirst depth and cut portions having a second depth, the first depthbeing lower than the second depth.

Typically, the main transverse groove crosses the circumferential cut ata cut portion having said first depth.

According to the present invention, for each transverse groove module,the tyre further comprises a secondary transverse groove. In turn, suchsaid secondary transverse groove comprises a tail and a substantiallyrectilinear portion parallel to the first-substantially rectilinearportion of the main transverse groove of the first shoulder portion.

Preferably, the secondary transverse groove has a width that is lowerthan a width of the main transverse groove.

Preferably, the tyre according to the invention comprises, for eachtransverse groove module, a main transverse groove and a secondarytransverse groove at least partially parallel to said main transversegroove.

Preferably, the main transverse groove and the secondary transversegroove are inclined by a third angle with respect to the radial plane,the third angle ranges from 3° to 10°.

According to a preferred embodiment, the third angle is the same as saidfirst angle.

Profitably, the central region comprises, for each transverse groovemodule, a main transverse groove and a secondary transverse groove.Advantageously, the secondary transverse groove is parallel to the maintransverse groove.

Preferably, the main and secondary transverse grooves are inclined by afourth angle with respect to a radial plane, said third angle rangingfrom 10° to 30°.

According to one embodiment of the invention, the second shoulder regioncomprises, for each transverse groove module, a main transverse groovethat is a mirror image of the main transverse groove of said firstshoulder region with respect to the tyre equatorial plane. In that case;the main transverse groove of the second shoulder region is preferablycircumferentially staggered of a distance with respect to the maintransverse groove of the first shoulder region.

Typically, the number of transverse groove modules is between 28 and 40.

Profitably, the transverse groove modules are circumferentiallyconsecutive.

Further characteristics and advantages of the present invention will beillustrated with reference to embodiments illustrated, by way of exampleand not of limitation, in the attached figures, wherein:—

FIG. 1 is a perspective view of a tyre according to a first embodimentof the present invention;

FIG. 2 is a partial plan view of a tread of the tyre shown in FIG. 1;

FIG. 3 is a partial cross section of the tyre of FIG. 1 along line 3-3in FIG. 2;

FIG. 4 is a partial cross section of the tyre of FIG. 1 along line 4-4in FIG. 2;

FIG. 5 is an enlarged view of a transverse groove module forming thetread of the tyre shown in FIG. 1;

FIG. 6 is a partial plan view of a tyre tread according to a secondembodiment of the present invention;

FIG. 7 is a partial cross section of the tyre of FIG., 6 along line 7-7in FIG. 6;

FIG. 8 is a partial cross section of the tyre of FIG. 1 along line 8-8in FIG. 6;

FIG. 9 is a partial plan view of a tyre tread according to a thirdembodiment;

FIG. 9 a is an enlarged view of a transverse groove module forming thetyre tread shown in FIG. 9;

FIGS. 10 a, 10 b, 11 a, 11 b show graphs relating to noise level outsideand inside a test car;

FIG. 12 shows a normalized sound pressure level graph as a function of avehicle speed; and

FIG. 13 shows a noise spectrum at about 80 Km/h.

The same reference numbers will be used in the various Figures forindicating the same parts or functionally equivalent components.

FIG. 2 is a partial plan view of a tread 3 of the tyre shown in FIG. 1in accordance with a first embodiment of the present invention. Tyre 1is of the asymmetric type; in other words, it has a pattern which isdifferent (i.e. asymmetric) on each side of an equatorial plane 2 (FIG.2).

The structure of the tyre is of the conventional type and comprises acarcass, a tread band located on the crown of said carcass, a pair ofaxially superimposed sidewalls terminating in beads reinforced with beadwires and corresponding bead fillers, for securing said tyre to acorresponding mounting rim. The tyre preferably also comprises a beltstructure interposed between the carcass and the tread band. Morepreferably, the tyre is of the type with a markedly flattened section,for example in the range from 0.65 to 0.30, where these figures expressthe percentage value of the ratio between the height of the cross rightsection of the tyre and the maximum chord of said section. In the art,this ratio is usually referred to as H/C.

The carcass is reinforced with one or more carcass plies associated tosaid bead wires, while the belt structure generally comprises two beltlayers, usually comprising metal cords, parallel to each other in eachlayer and crossing over those of the adjacent layers, preferablyinclined symmetrically with respect to the equatorial plane, andradially superimposed on each other. Preferably, the belt structure alsocomprises a third belt layer, in a radially outermost position, providedwith rubberized cords, preferably textile cords, orientedcircumferentially, i.e. with a disposition at substantially zero degreeswith respect to said equatorial plane.

Tyre 1 has a tread 3 of elastomeric material, provided with threecircumferential grooves 4, 5 and 6. Grooves 4 and 6 divide a treadcentral region 7 from two shoulder regions 8 and 9, located on the leftand on the right of the equatorial plane 2, respectively. Shoulderregion 8 will be also referred to as “external shoulder region”.Similarly, shoulder region 9 will be also referred to as “internalshoulder region”. The terms “internal” and “external” are referred to avehicle on which the tyre is mounted: “internal” stands for “internalwith respect to the vehicle”, while “external” stands for “externallywith respect to the vehicle”. The tread central region 7 of tyre 1comprises the central circumferential groove 5.

Preferably, shoulder circumferential groove 6 has a width less than thatof circumferential grooves 4 and 5. Unless otherwise indicated, a widthof a groove, a cut, a notch or similar elements is a measure taken onthe top thereof, in correspondence of the tread surface. The width ofshoulder circumferential groove 6 is preferably between 10.0 mm and 14.0mm. The maximum depth of lateral circumferential groove 6 is preferablybetween 5.5 mm and 8.5 mm. Circumferential groove 4 has a widthpreferably between 13.0 mm and 22.0 mm. The maximum depth ofcircumferential groove 4 is preferably between 5.5 mm and 9.0 mm.Preferably, the bottom of circumferential groove 4 has a centralcircumferential raising portion 4 a which has the function of stiffeningthe circumferential groove 4. Thus, at the circumferential raisingportion 4 a, the circumferential groove 4 is about 4.5-8.0 mm depth.According to a preferred embodiment, circumferential grooves 4 and 5have substantially the same shape and dimensions. In such a preferredembodiment, also groove 5 is provided with a raising portion 5 a similarto raising portion 4 a of groove 4.

The tread 3 of FIG. 2 is formed by a number p, typically from 28 to 40,of transverse groove modules 10. Said number p indicates the number ofpitches present in the tread pattern of the present invention. A singlemodule 10 of the tread of FIG. 2 is shown in FIG. 5 and comprises atread central portion 7′, a first shoulder portion 8′ and a secondshoulder portion 9′.

In the present description, each angle—which is used to indicate theinclination of a given tread pattern element is intended to becalculated as the angle defined between a radial plane of the tyre andthe plane said given tread pattern element belongs to, said angle beingobtained by a counter-clockwise rotation of the plane of the given treadpattern element towards the radial plane of the tyre. Internal shoulderregion 9 will be described here below. It comprises a plurality of maintransverse grooves 12 and a plurality of secondary transverse grooves13. The main transverse groove 12 comprises a rectilinear portion 12 ainclined by an angle β of about 3°-10° (preferably 7°-9°, morepreferably about 8°) with respect to a radial plane and a tail 12 b thatis substantially at about 45° with respect to a radial plane. The topend of rectilinear portion 12 a communicates with groove 6 by a reduceddepth rectilinear portion 12 c. Thus, the main transverse groove 12 hasa depth ranging from about 2.0-4.0 mm (at 12 c) to about 4.0-8.0 mm (inthe first portion of the rectilinear portion, 12 a) to zero (at the endof tail 12 b). The width of rectilinear portions 12 a and 12 c of themain transverse groove 12 is about 4.0-8.0 mm. Similarly, the secondarytransverse groove 13 comprises a rectilinear portion 13 a, inclinedpreferably by the same angle β as above, and a tail 13 b. The secondarytransverse groove 13 has a depth ranging from about 4.0-8.0 mm (in thefirst portion of the rectilinear portion 13 a) to zero (at the end oftail 13 b). The width of rectilinear portion 13 a of the main transversegroove 13 is about 2.5-8.0 mm. The secondary transverse groove 13further comprises a notch 13 c having the same width of the rectilinearportion 13 a (about 2.5-8.0 mm) and a depth of about 2.0-8.0 mm. Thenotch 13 c could be separated from the top end of the rectilinearportion 13 a as shown in FIG. 2 and FIG. 3.

In the shoulder region 9 a number of shoulder blocks are formed betweentwo main transverse grooves. The number of shoulder blocks in region 9ranges from 28 to 40.

The tread central region 7 of tyre 1 will now be described in detail. Assaid above, it comprises the central circumferential groove 5 dividingthe central region 7 into two parts.

In the first part (the one adjacent to circumferential groove 6) of thecentral region 7, main transverse grooves 22 and secondary transversegrooves 23 are provided. The main transverse grooves 22 extend fromcircumferential groove 5 to circumferential groove 6 and are inclined byan angle γ which is preferably greater than β. Preferably, γ=10°-30°(more preferably, γ=about 15°-20°, still more preferably γ=16°-18°) withrespect to a radial plane. The width of main transverse grooves 22 ispreferably the same as main transverse groove 12. The main transversegroove 22 has, in a middle part thereof (22 a), a depth of about 3.0-8.0mm; the main transverse groove 22 has, in end parts thereof (22 b, 22c), a depth of about 4.0-8.0 mm. The secondary transverse grooves 23 arepreferably inclined by the same angle γ as the main transverse grooves22. Preferably, the secondary transverse grooves 23 have the same widthof secondary transverse grooves 13 and have a depth of about 2.0-8.0 mm.In a first embodiment (the one of FIGS. 2 and 3) the secondarytransverse groove 23 comprises two separate secondary transverse grooveportions 23 a, 23 b. Groove portion 23 a communicates with the centralcircumferential groove 5 and groove portion 23 b communicates withcircumferential groove 6. In a second alternative embodiment (notshown), the two separate secondary transverse groove portions 23 a, 23 bare connected together, preferably by a sipe.

A number of first central blocks are provided between two maintransverse grooves 22. The number of first central blocks ranges between28 and 40. Preferably, the number of first central blocks is the same asthe number of blocks in the shoulder region 9.

In the second part (the one between circumferential grooves 4 and 5) ofthe central region 7, main transverse grooves 32 and secondarytransverse grooves 33 are provided. Preferably, both the main andsecondary transverse grooves 32 and 33 are inclined of the same angle γas transverse grooves 22 and 23, respectively. Preferably, the maintransverse groove 32 has the same width of transverse groove 22 and hasa depth of about 2.0-8.0 mm. According to a preferred embodiment (shownin FIG. 2), the main transverse groove 32 comprises two separateportions 32 a, 32 b connected by a transverse sipe 32 c. Sipe 32 ccrosses the equatorial plane of the tyre and has a depth of about2.0-6.0 mm. Preferably, sipe 32 c has a width of about 1.0-2.0 mm.Preferably, secondary transverse groove 33 extends in proximity ofcentral circumferential groove 5. Preferably, secondary transversegroove 33 has a depth of about 2.0-8.0 mm. Preferably, secondarytransverse groove 33 has a width of about 2.5-8.0 mm. Preferably, thecircumferential groove 5 is provided with a circumferential raisingportion 5 a which contributes in stiffening the circumferential groove5. According to a preferred embodiment of the present invention, thecircumferential raising portion 5 a of circumferential groove 5 hasdepressions 5 b in correspondence of the main transverse grooves 22 and32.

A number of second central blocks are provided between two maintransverse grooves 32. The number of second central blocks rangesbetween 28 and 40. Preferably, the number of second central blocks isthe same as the first central blocks as well as the blocks in theshoulder region 9.

The external shoulder region 8 will be now described in detail. Theexternal shoulder region 8 comprises: a circumferential cut 15, aplurality of main transverse grooves 42 and a plurality of secondarytransverse grooves 43.

In the present description, by “circumferential cut” it is meant a notchrunning circumferentially and having a width not higher than 35% of thewidth of any circumferential groove in the tyre. Preferably, thecircumferential cut width is less than 30% (and still more preferablyless than about 25%) of the width of any circumferential groove.Preferably, the circumferential cut width is of from 10% to 30% of thewidth of any circumferential groove.

The secondary transverse groove 43 comprises a substantially rectilinearportion 43 a and an external tail 43 b which is substantially at 45°with respect to a radial plane. Preferably, the substantiallyrectilinear portion 43 a is inclined by an angle α. Preferably, α rangesfrom 3° to 10°, more preferably between about 7° and 9°. According to apreferred embodiment, a has the same value of β: in other words,secondary transverse grooves 13 and 43 are equally inclined with respectto a radial plane. Indeed, the substantially rectilinear portion 43 aterminates with an end portion that is slightly curve. The secondarytransverse groove 43 has a depth ranging from about 4.0-8.0 mm (in thefirst part of the rectilinear portion 43 a) to zero (at the end of tail43 b). The width of substantially rectilinear portion 43 a of thesecondary transverse groove 43 is about 2.5-8.0 mm.

The main transverse grooves 42 of external shoulder 8 comprises (fromleft to right in FIGS. 2 and 5): a tail 42 a, a first substantiallyrectilinear portion 42 b, a curve portion 42 c and a secondsubstantially rectilinear portion 42 d. Tail 42 a is similar to tail 12b but it is preferably directed in the opposite direction. Preferably,tail 42 a is more inclined than the first rectilinear portion 42 b. Thefirst substantially rectilinear portion 42 b is preferably inclined bythe same angle α mentioned above. According to a preferred embodiment,the first substantially rectilinear portion 42 b is inclined as theportion 12 a. The first substantially rectilinear portion 42 b has awidth between about 4.0 mm and 8.0 mm and it has a maximum depth (inproximity of circumferential cut 15) of about 4.0 mm to 8.5 mm. Thecurve portion 42 c connects the first and second substantiallyrectilinear portions 42 b and 42 d. Preferably, curve portion 42 c hasthe same width and depth of rectilinear portion 42 b. The radius ofcurvature of the curve portion 42 c is between 15.0 and 30.0 mm.Preferably, the curve portion 42 c crosses the circumferential cut 15.The second rectilinear portion 42 d is inclined by an angle δ withrespect to a radial plane of the tyre. Angle δ is preferably of about105°-130°, more preferably between 110° and 120° and still morepreferably of about 115°. Preferably, the angle comprised between thefirst and second substantially rectilinear portions is higher than 90°.The second rectilinear portion 42 d, preferably, has the same width anddepth of the first rectilinear portion 42 b (width 4.0-8.0 mm;depth=4.5-8.5 mm). Preferably, the first rectilinear portion 42 b andthe second rectilinear portion 42 d converge in correspondence of thecircumferential cut 15.

In a preferred embodiment of the present invention (FIGS. 2 and 4), thetop end of the second substantially rectilinear portion 42 d isconnected to the circumferential groove 4 through a slightly curveportion 42 e which has a reduced depth with respect to the rectilinearportion 42 d. The depth of curve portion 42 e is about 1.0-4.0 mm,preferably about 2.0 mm. Preferably, the curve portion 42 e has a widthof from 4.0 mm to 8.0 mm. As it is shown in FIG. 2 and FIG. 4,depressions 4 b are provided in the raising portion 4 a for “connecting”the curve portion 42 e to the substantially rectilinear portion 32 a inthe central region.

Alternatively, according to a further embodiment of the presentinvention (shown in FIGS. 6, 7 and 8), the main transverse groove 42 isnot provided with a curve portion 42 e and the second substantiallyrectilinear portion 42 d smoothly terminates at about 4.0-10.0 mm fromgroove 4. Preferably, the second substantially rectilinear portion 42 dterminates at a distance (L5) from about 5% to about 40% of 12, morepreferably from about 15% to about 30% of L2. Preferably, the secondsubstantially rectilinear portion 42 d terminates at a distance fromabout 30% to about 40% of the width of groove 4.

Preferably, the distance between two circumferentially consecutive(adjacent) main grooves 42 is substantially constant. Preferably, thedistance between two circumferentially consecutive (adjacent) maingrooves 42 is from about 25% and 35% of the tyre diameter. Said aspectpositively contributes to the noiseness and longitudinal stiffnessperformances of the tyre of the invention.

The circumferential cut 15 is provided in the tyre according to thepresent invention in order to contribute to the hinge effect in theshoulder region. Profitably, circumferential cut 15 has a width of about1.0-3.0 mm. The depth of the circumferential cut 15 varies from areduced depth of about 1.0 to 4.0 mm to a full depth of about 4.0-7.5mm. The parts (15 a) of circumferential cut 15 that have a reduced depthare those in correspondence of main transverse grooves 42; the parts (15b) of circumferential grooves that have a full depth are those inproximity of secondary transverse grooves 43. Preferably, secondarytransverse grooves 43 do not cross the cut portions 15 b.

The number of blocks in the external shoulder (when each block isdefined between two main transverse grooves 42) ranges from 28 to 40.Thus, according to a preferred embodiment of the present invention, thepitch of the tread pattern is the same in the two shoulder regions aswell as in the central region. The most axially external part ofexternal shoulder region 8 (i.e. the part which is external to thecircumferential cut 15—the part on the left in FIG. 2) has a patternsimilar to that of the internal shoulder region 9 with secondarytransverse grooves 43, 13 that are arranged between, and are preferablysubstantially parallel to, main transverse grooves 42, 12 respectively.

This arrangement of transverse grooves (12, 13 in the internal shoulderregion 9 and 42, 43 in the external shoulder region—all of thembelonging to the same transverse groove module 10) is advantageous inreducing the noise of the tyre tread pattern of the present inventionsince the grooves belonging to one shoulder are circumferentiallystaggered with respect to the grooves belonging to the opposite shoulderso that they enter the tyre footprint area at different time instants,thereby splitting the tread noise on a wide range of frequencies andfavorably improving the noiseness performance of the tyre.

The other (axially inner) part of the external shoulder region 8 (theone between circumferential cut 15 and circumferential groove 4) isprovided with the highly inclined main transverse grooves 42. If themain transverse grooves of the tread pattern are considered, it can benoted that, in combination with the transverse grooves 22 of theremaining central portion 7 and with the transverse grooves 12 of theinternal shoulder portion 9, they form a substantially continuous wavepattern which starts at one tyre shoulder and reaches the opposite one.

In considering a plan view (as shown in FIG. 2), the blocks which aredefined among the circumferential cut 15, the adjacent circumferentialgroove 4 and two circumferentially consecutive main transverse grooves42 are substantially rhomboid shaped, whilst the blocks defined amongthe circumferential cut 15, the external tyre shoulder and twocircumferentially consecutive main transverse grooves 42 aresubstantially rectangular in shape.

The width of the tyre pattern according to the present invention isindicated with L (L is generally ≧about 200 mm). The external shoulder 8has a width L1 which ranges from about 25% to 35% of L. In particular,the region between circumferential cut 15 and circumferential groove 4has a width L2 that ranges from 20% to 35% of L1. The internal shoulder9 has a width L3 which is less than L1 and is preferably between about20% and 30% of L. Finally, the central region 7 has a width L4 betweenabout 25 and 40% of L.

The external shoulder of the tyre according to the present invention issubstantially stiff; but the circumferential cut 15 provides a positiveand controlled flexibility of the tyre shoulder in a plane parallel tothe equatorial plane and passing through said circumferential cut.Circumferential cut 15 is not to be considered as a circumferentialgroove and does not contribute to aquaplaning performances. Theaquaplaning performances are highly increased by the presence of themain transverse grooves 42 in combination with the circumferentialgrooves 4, 5, 6. As mentioned above, circumferential cut 15 provides a“hinge effect” which results in a larger contact area so that a largerrubber area is in contact with the rolling surface and thus both gripand handling performances are advantageously increased.

FIG. 9 is a partial plan view of a tread of a tyre in accordance with athird embodiment of the present invention. Reference numbers similar tothose of FIGS. 2 to 8 have been used in FIG. 9 for indicating functionalequivalent components. It will be immediately recognized that the treadpattern of FIG. 9 is substantially symmetrical and it can be classifiedas a “directional” pattern whose rolling direction is indicated by arrowF.

In details, the tread of FIG. 9 comprises two circumferential grooves 4and 6. Circumferential grooves 4 and 6 divide a tread central region 7from two shoulder regions 8 and 9. A detailed description of shoulderregion 8 will not be repeated because it substantially corresponds toexternal shoulder region 8 of FIGS. 2 to 6.

As clearly indicated in FIG. 9 a, the transverse groove module 10′ ofthe embodiment shown in FIG. 9 comprises a first shoulder portion 8″,which substantially corresponds to the first shoulder portion 8′ ofmodule 10, and a second shoulder portion 9″ which comprises a maintransverse groove 42′ and a secondary transverse groove 43′.

Preferably, main transverse groove 42′ and secondary transverse groove43′ of second shoulder portion 9″ are mirror-like elements—with respectto the tyre equatorial plane 2—of main transverse groove 42 andsecondary transverse groove 43 of the first shoulder portion 8″ (i.e.main transverse groove 42′ and secondary transverse groove 43′ of secondshoulder portion 9″ are mirror images of main transverse groove 42 andsecondary transverse groove 43 of the first shoulder portion 8″ withrespect to the tyre equatorial plane 2).

More preferably, the main transverse groove 42′ of second shoulderportion 9″ of module 10′ is circumferentially staggered of a distance Xwith respect to the main transverse groove 42 of the first shoulderportion 8″.

Preferably, said distance X is comprised from about 5% to about 25% of apitch length Y circumferentially measured. Pitch-length Y is indicatedin FIG. 9 a.

Preferably, circumferential grooves 4 and 6 substantially correspond togrooves 4 and 6 of FIGS. 2 to 6 and will not be described in details.

The central region 7 comprises main transverse grooves 32, 32′ andsecondary transverse grooves 33, 33′. The main transverse grooves 32,32′ extend from circumferential grooves 4, 6 respectively and arepreferably inclined by the same angle γ which has been defined above.The width and depth of main transverse grooves 32, 32′ in the embodimentof FIG. 9 are the same as those of main transverse grooves 32 accordingto the embodiments shown in FIGS. 2-8. It will be recognized that maintransverse grooves 32, 32′ are substantially short projections ofmain-transverse grooves 42, 42′-respectively. The secondary transversegrooves 33, 33′ are preferably inclined by the same angle γ as the maintransverse grooves 32, 32′. Preferably, the secondary transverse grooves33, 33′ have the same width and depth of the main transverse grooves 32,32′ respectively. The secondary transverse grooves 33, 33′ communicatewith the circumferential grooves 4, 6 respectively and are arrangedbetween main transverse grooves 32, 32′ respectively.

It can be pointed out that the tread pattern of FIG. 2 or FIG. 6, whichpossesses only three longitudinal (circumferential) grooves, providesthe tyre with a lateral stiffness which is higher than that of asimilar-tyre having four longitudinal grooves, while the aquaplaningperformance is even higher than that of a similar tyre having fourlongitudinal grooves, while ensuring very good grip, braking, noisenessand wear performances.

Tyres having a tread pattern according to the first embodiment (FIGS.1-5) were subjected to comparative tests with tyres manufactured by thesame Applicant and commercially known as “Pzero Rosso®”. Saidcomparative tyres have been chosen because they are high performancetyres with excellent characteristics and have been approved for fast andvery-high performance sport cars. The rear wheel tyres according to thepresent invention has a size of 265/35 R18; the front wheel tyresaccording to the present invention had a size of 225/40 R18. Theinflation pressure was 2.5 bar for the front wheels and 3.0 bar for therear wheels. The comparative tyres had the same structure, sizes andinflation pressures of the invention tyres.

A car, model “Porsche 996”, was first equipped with four tyres accordingto the invention and then with four comparative tyres.

Aquaplaning tests were carried out along straight road sections andaround bends, together with braking tests on dry and wet road surfaces,tests for noise inside and outside the car, and comfort tests.

The aquaplaning test along straight road sections was carried out alonga straight section of smooth asphalt, of predefined length (100 m), witha layer of water of predefined constant height (7-mm) which wasautomatically restored after each test vehicle had passed by. Thevehicle entered at a constant speed (approximately 100 km/h) inconditions of perfect grip and accelerated until the conditions of totalloss of grip occurred.

The aquaplaning test around bends was carried out along a road sectionwith smooth and dry asphalt, around a bend with a constant radius (100m), having a predefined length and comprising, along a final section, azone of predefined length (20 m) flooded with a layer of water ofpredefined thickness (6 mm). The test was carried out at a constantspeed for different speed values.

The braking test was carried out both on a dry surface and on a wetsurface where a rain fall of 60 mm of water per hour was simulated. Thedry braking test consisted in decreasing the speed, of the test car from100 Km/h to 5 Km/h; the wet braking test consisted in decreasing thespeed of the test car from 80 Km/h to 5 Km/h. The test was carried outalong a straight road section and braking distances were measured.

The results of the aquaplaning and braking tests are shown in Table Iwhere the values assigned are expressed as a percentage against thevalues of the comparative tyre fixed at 100. Thus, values higher than100 indicate an improvement with respect to the comparative tyres.

TABLE I Car with Car with tyres comparative according to the tyresinvention Aquaplaning along straight 100 102.4 sections (“straightaquaplaning”) Aquaplaning around bends 100 113.0 (“lateral aquaplaning”)Dry braking test 100 104.0 Wet braking test 100 101.0

As it can be inferred from Table 1, the car equipped with tyresaccording to the present invention gave very good performances in allconditions. In particular, excellent performances were obtained inlateral aquaplaning.

The comfort was evaluated in terms of the overall sensations perceivedby a test driver compared to the capacity for the tyre to absorb theroughness of the road surface.

The results of the comfort test are shown in Table II where the valuesassigned are expressed as a percentage against the values of thecomparative tyre fixed at 100. As it can be seen, the test driverperceived the same sensations by driving the car with the comparativetyres and the tyres according to the invention.

TABLE II Car with tyres Car with according to the comparative tyresinvention Comfort 100 100

The noise tests were carried out both indoors and outdoors.

The indoor tests were carried out in an externally sound-proofed chamber(semianechoic chamber) by using the abovementioned car equipped firstwith a tyre according to the invention and then with a comparative tyre,keeping the tyre in contact with a rotating drum made to rotate atdifferent speeds. Microphones were arranged inside and outside the carin order to measure, respectively, the internal noise and externalnoise.

The outdoor test was carried out along a straight section equipped withmicrophones. The car entered the section at a predefined speed of entry,after which the engine was switched off and the noise outside the car inneutral gear was measured.

FIGS. 10 a, 10 b, 11 a and 11 b show the graphs relating to the noiselevel in dB(A) outside (FIG. 10 a, 10 b) and inside (FIG. 11 a, 11 b)the test car in relation to the speed (km/h) ranging from 20 to 150km/h. The curves A1 and A2 relate to the comparative tyre PZero Rosso®265/35ZR18; the curves A3 and A4 relate to the comparative tyre PZeroRosso® 225/40ZR18; the curves B1 and B2 relate to the tyre with a treadaccording to the first embodiment of the present invention while thecurves B3 and B4 relate to the tyre with a tread according to the secondembodiment of the present invention. PZero Rosso® 265/35ZR18 and thetyre with the first embodiment of tread pattern were mounted on the rearleft of said car; PZero Rosso® 225/40ZR18 and the tyre with the secondembodiment of tread pattern were mounted at the front left of said car.

With reference to FIG. 10 a, it may be noted that the tyre according tothe invention had an external noise level which was lower than that ofthe comparative tyre at speeds lower than about 95 Km/h and which wassubstantially equivalent to it at speeds higher than 95 Km/h. Withreference to FIG. 10 b, it may be noted that the tyre according to theinvention had an external-noise level which was lower than that of thecomparative tyre at speeds higher than about 85 Km/h and which wassubstantially equivalent to it at speeds lower than 85 Km/h. Withreference to FIG. 11 a, it may be noted that the tyre according to theinvention had an internal noise level which was generally lower than orequal to that of the comparative tyre. Finally, with reference to FIG.11 b, it may be noted that the tyre according to the invention had aninternal noise level which was lower than that of the comparative tyreat speeds higher than about 85 Km/h and which was higher to it at speedshigher than 85 Km/h.

FIG. 12 shows a normalized sound pressure level (SPL) graph as afunction of a vehicle speed and FIG. 13 shows a noise-spectrum at 80Km/h. Curves A, A1 relate to the comparative tyre, whilst curves B, B1relate to the tyre according to the present invention. In both cases,the tyre had a size 265/35ZR18 mounted on a 8Jx18 rim.

The graphs show the result of the so-called “coast-by-noise” tests (ISO362-1981, Amendment 1, published 1985) carried out with the cardescribed above in accordance with the standard ISO 10844. During thesetests the reference speed was 80 km/h.

FIG. 12 shows that the tyre according to the invention had proved to beless noisy than the comparative-tyre. In particular, as it can bederived from FIG. 13, a reduction of noise was experienced atfrequencies higher than about 500 Hz. Also in frequencies ranges 115-145Hz and 183-230 Hz a big reduction of noise was detected.

Furthermore, lateral and longitudinal stiffness of a tyre according tothe first embodiment of the present invention was calculated by,computer simulation. The tread was finite element modeled as a rubberplate having a thickness equal to that of the tread band. As the tyrecarcass structure, is known, the contact area is experimentallyestablished for a number of loads. In the finite element modeled plate,an area having a shape correspondent to the contact area is considered.All the nodes that are in contact with the ground are constrained sothat they become fixed. All the other nodes (those that are not incontact with the ground) are moved in a first direction X (resulting ina shift S_(X) in such a first direction) and in a second direction Y(resulting in a shift S_(Y) in such a second direction). Thus, itbecomes possible to calculate the forces which are requested for movingthe nodes into the first and second directions (F_(X) and F_(Y),respectively). Finally, the stiffness in the first direction X(longitudinal stiffness) is given by K_(X)=F_(X)/S_(X) and the stiffnessin the second direction Y (lateral stiffness) is given byK_(Y)=F_(Y)/S_(Y).

The results of the stiffness computer simulation are shown in Table IIIwhere the values assigned are expressed as a percentage against thevalues of the comparative tyre fixed at 100. Thus, values higher than100 indicate an improvement with respect to the comparative tyre.

TABLE III Tyre according to Comparative tyre the invention Longitudinalstiffness (K_(X)) 100 112.6 Lateral stiffness (K_(Y)) 100 112.3

Thus, the tyre according to the present invention has shown a highstiffness.

Finally, a handling test in dry surface conditions was carried out alongpredefined sections. For the handling test a car Ferrari, model 575, wasused. For this test, the rear wheel tyres according to the presentinvention had a size of 305/35 R19; the front wheel tyres according tothe present invention had a size of 255/40 R19. The inflation pressurewas 2.5 bar for the front wheels and 3.0 bar for the rear wheels. Thecomparative tyres Pzero Rosso® had the same structure, sizes andinflation pressures of the invention tyres.

In order to evaluate the tyre behavior, the test driver simulated somecharacteristic maneuvering (change of lane, entering a bend, leaving abend, for example) carried out at constant speed, in acceleration and indeceleration. Then the test driver judged the tyre behavior and assigneda score depending on the tyre performance during said maneuvering.

The handling is generally divided into two voices (soft handling andhard handling) depending on the type of manoeuvre carried out by thetest driver. The soft handling relates to the use of the tyre undernormal driving conditions, i.e. in conditions of normal speed and goodtransversal grip. On the contrary, the hard handling tests describe thebehaviour of the tyre at the limit of adherence, i.e. under extremedriving conditions. In the latter case the test driver executesmanoeuvres which an average driver might be forced to carry out in thecase of unforeseen and hazardous circumstances: sharp steering at highspeed, sudden changing of lanes to avoid obstacles, sudden braking, andthe like.

Two different types of tests were carried out: behaviour at normal speed(soft handling) and behaviour at the limit of adherence (hard handling).

As far as the soft handling tests were concerned, the test driverassessed: emptiness in the centre, that is the delay and the degree ofresponse of the vehicle to small steering angles; the promptness ofresponse to the steering coming into a bend; the progressiveness ofresponse to the steering travelling in a bend; centering in a bend, thatis the tyre capacity to keep the vehicle on a bend with a constantradius without continuous steering corrections; realignment, that is thecapacity of the tyre to allow the vehicle to return to a rectilineartrajectory at the exit of a bend with contained and dampened transversesoscillations.

As far as the hard handling tests were concerned, the test driverassessed: the force on the steering wheel when turning violently; thepromptness of insertion, that is the behaviour of the tyre in transitionat the entrance of the bend taken at the limit speed; the balancing,that is the degree of over-steering or under-steering of the vehicle;the yield, that is the tyre capacity to absorb a strong fast transfer ofthe load as a consequence of a sudden change of lane without excessivedeformation, and therefore without compromising vehicle stability andcontrollability; release in a bend, that is the tyre capacity to dampenthe effects of instability resulting from the sudden release of theaccelerator during a bend taken at the limit speed; controllability,that is the tyre capacity to maintain and/or return the vehicle to thetrajectory after the loss of adherence.

Table IV sums up the test driver's score sheet for the tyrescontrollability. The results of said tests are expressed by means of anevaluation scale representing the subjective opinion expressed by thetest driver through a point system. The values reproduced in thefollowing table represent a mean value between those obtained in severaltest sessions (5-6 tests, for example) and given by several test drivers

TABLE IV Test carried out Car with Car with by the test tyres accordingto comparative Handling drivers the invention tyres Steering Emptinessat the 7 6.5 behavior center (Soft handling) Promptness 7 6Progressiveness 7 6 Centring in bend 7.5 6 Realignment 7 6 Behavior atPromptness of 7 6 limit (Hard insertion handling) Balancing 7 6 Releasein bend 7 6 Understeering 7 6.5 Oversteering 7.5 6.5 Controllability 7.56.5

1-27. (canceled)
 28. A tyre for a motor vehicle comprising a treadhaving an overall width and comprising first and second circumferentialgrooves which separate a central region from first and second shoulderregions, comprising: a circumferential cut in said first shoulder regionat a distance from said first circumferential groove; and a plurality ofcircumferentially repeated transverse groove modules, wherein a firstshoulder portion of each transverse groove module comprises at least onemain transverse groove comprising: a first substantially rectilinearportion inclined by a first angle with respect to a radial plane; asecond substantially rectilinear portion inclined by a second angle withrespect to said radial plane and arranged between said circumferentialcut and said first circumferential groove; and a first curve portionconnecting said first and said second substantially rectilinearportions.
 29. The tyre according to claim 28, wherein said maintransverse groove further comprises a second curve portion connectingsaid second substantially rectilinear portion to said firstcircumferential groove.
 30. The tyre according to claim 29, wherein saidsecond curve portion has a depth that is lower than a depth of saidsecond substantially rectilinear portion.
 31. The tyre according toclaim 28, wherein said first shoulder region has a width that is 25% to35% of said overall width.
 32. The tyre according to claim 28, whereinsaid distance between said circumferential cut and said firstcircumferential groove is 25% to 35% of a width of said first shoulderregion.
 33. The tyre according to claim 28, wherein said secondsubstantially rectilinear portion ends at a distance from said firstcircumferential groove that is about 5% to about 40% of the distancebetween said circumferential cut and said first circumferential groove.34. The tyre according to claim 28, wherein said second substantiallyrectilinear portion ends at a distance from said first circumferentialgroove that is about 30% to 40% of a width of said first circumferentialgroove.
 35. The tyre according to claim 28, wherein said first angle is3° to 10°.
 36. The tyre according to claim 28, wherein said first angleis 7° to 9°.
 37. The tyre according to claim 28, wherein said secondangle is 105° to 130°.
 38. The tyre according to claim 28, wherein saidsecond angle is 110° to 120°.
 39. The tyre according to claim 28,wherein said main transverse groove further comprises a tail connectedto said first substantially rectilinear portion.
 40. The tyre accordingto claim 28, wherein said circumferential cut comprises cut portionshaving a first depth and cut portions having a second depth, said firstdepth being lower than said second depth.
 41. The tyre according toclaim 40, wherein said main transverse groove crosses saidcircumferential cut at a cut portion having said first depth.
 42. Thetyre according to claim 28, further comprising, a secondary transversegroove for each transverse groove module.
 43. The tyre according toclaim 42, wherein said secondary transverse groove comprises a tail anda substantially rectilinear portion parallel to said first substantiallyrectilinear portion of said main transverse groove of said firstshoulder portion.
 44. The tyre according to claim 42, wherein saidsecondary transverse groove has a width that is lower than a width ofsaid main transverse groove.
 45. The tyre according to claim 28, whereinsaid second shoulder region comprises a main transverse groove and asecondary transverse groove at least partially parallel to said maintransverse groove for each transverse groove module.
 46. The tyreaccording to claim 45, wherein said main transverse groove and saidsecondary transverse groove are inclined by a third angle with respectto said radial plane, said third angle ranging from 3° to 10°.
 47. Thetyre according to claim 46, wherein said third angle is the same as saidfirst angle.
 48. The tyre according to claim 28, wherein said centralregion comprises a main transverse groove and a secondary transversegroove for each transverse groove module.
 49. The tyre according toclaim 48, wherein said secondary transverse groove is parallel to saidmain transverse groove.
 50. The tyre according to claim 48, wherein saidmain and secondary transverse grooves are inclined by a fourth anglewith respect to a radial plane, said fourth angle ranging from 10° to30°.
 51. The tyre according to claim 28, wherein said second shoulderregion comprises for each transverse groove module, a main transversegroove that is a mirror image of the main transverse groove of saidfirst shoulder region with respect to the tyre equatorial plane.
 52. Thetyre according to claim 51, wherein the main transverse groove of thesecond shoulder region is circumferentially staggered a distance withrespect to the main transverse groove of said first shoulder region. 53.The tyre according to claim 28, wherein the number of transverse groovemodules is 28 to
 40. 54. The tyre according to claim 28, wherein thetransverse groove modules are circumferentially consecutive.